The present invention relates to a refrigerating machine and, more particularly, to a refrigerating machine capable of absorbing hot air entering a refrigerating chamber and absorbing moisture in the hot air to increase the refrigerating effect and refrigerating efficiency in the refrigerating chamber.
A typical refrigerating system generally includes a compressor, a condenser, an expansion valve, and an evaporator connected to each other by a piping to form a closed loop in which a coolant circulates. The evaporator is located in a refrigerating chamber. The liquid coolant is delivered by the compressor into the evaporator to absorb the heat in the refrigerating chamber through low-temperature evaporation. Thus, the refrigerating chamber is in a low temperature state to refrigerate food or objects in the refrigerating chamber. Early evaporators are of air-cooled type and include a circulating fan to proceed with forced draught of air, such that heat change can be conducted between the air in the refrigerating chamber and the heat changer tube in the air-cooled evaporator. Since the heat generated due to operation of the motor of the evaporator and friction of the air currents outputted by the circulating fan causes an increase in the temperature in the refrigerating chamber, the refrigerating system must operate continuously to reduce the temperature, leading to considerable consumption of electricity. Furthermore, temperature imbalance exists due to a temperature difference in the order of 4 degrees Celsius between the air inlet and the air outlet.
Recently, air-cooled evaporators have been replaced by tube-cooled evaporators due to the above disadvantages. A tube-cooled evaporator generally includes a tube mounted on an inner top face of a refrigerating chamber and a plurality of radially spaced fins on an outer periphery of the tube. Two faces of each fin and the outer periphery of the tube provide cold energy for heat exchange with the food in the refrigerating chamber. Since the tube with fins is fixed to every area on the inner top face of the refrigerating chamber, the cold air descends naturally to provide a thorough, even refrigeration effect. Thus, no circulating fans are required if the refrigerating chamber is equipped with a tube-cooled evaporator, effectively solving the disadvantages of the air-cooled evaporators.
Since the temperature of the faces of each fin and the outer periphery of the tube is in a range between minus 20 degrees Celsius and minus 50 degrees Celsius for heat exchange with the food in the refrigerating chamber, the hot air enters the refrigerating chamber while the door of the refrigerating chamber is opened, and the moisture in the hot air and the water content in the food frost on the faces of the fins and the outer periphery of the tube due to condensation. The frost accumulates to form an insulating layer adversely affecting the heat exchange efficiency. Thus, timely defrosting the faces of the fins and the outer periphery of the tube is required for maintaining normal operation of the refrigerating system. Current defrosting methods include stopping the compressor, hot gas defrosting, and defrosting by sprinkling water. These methods will result in a wet floor and the risk of injury by the falling frost.
Thus, it is an important issue to absorb the hot air entering the refrigerating chamber, the moisture in the hot air, and the water content in the object to be refrigerated for the purposes of increasing the refrigerating effect and refrigerating efficiency while increasing the defrosting efficiency.